1. Field of the Invention
The present invention relates to an electrophotographic image forming device, such as an electrophotographic printer, and an exchange method of a photosensitive belt and a transfer belt comprising the same. In particular, the present invention relates to an electrophotographic image forming device having a simple structure and an exchange method of a photosensitive belt and a transfer belt, which can be easily carried out.
This application is based on Japanese Patent Application No. Hei 11-105957, the contents of which are incorporated herein by reference.
2. Description of the Related Art
A conventional electrophotographic image forming device, such as an electrophotographic printer, comprises a photosensitive belt. The photosensitive belt is consumable; therefore, the photosensitive belt must be exchanged, depending on its use period or the printing frequency. FIG. 6 shows an internal constitution of a conventional electrophotographic printer viewed from the front side.
In the conventional electrophotographic printer, a tray 29a for storing recording media, such as printing paper, and some pairs 32 of transferring rollers for transferring the recording medium are provided in the body 21. The pair 32 of transferring rollers is provided with the body 21 so that each of the rollers rotates.
In addition, a photosensitive belt 22 and a belt driver 31 for the photosensitive belt 22 are provided in the body 21. The belt driver 31 comprises four driving rollers 23, 24, 25, and 26. The three rollers 23, 24, and 25 among the driving rollers 23, 24, 25, and 26 are located so as to form a triangle. Another driving roller 26 is located between the driving rollers 24 and 25. The longitudinal directions of these driving rollers 23, 24, 25, and 26 are parallel. The photosensitive belt 22 is located so as to contact with the surface of the driving rollers 23, 24, 25, and 26 while being taut. Moreover, the driving roller 25 can shift toward the driving roller 24. When the driving roller 25 shifts toward the driving roller 24, the tension of the photosensitive belt 22 loosens.
A developing roller 27 is located opposite to the driving roller 26 with respect to the photosensitive belt 22 so that the developing roller 27 and driving roller 26 sandwich the photosensitive belt 22. The developing roller 27 is provided with the body 21 so as to be able to shift downwardly. Furthermore, a transfer roller 28 is located opposite to the driving roller 23 with respect to the photosensitive belt 22 so that the transfer roller 28 and the driving roller 28 sandwich the photosensitive belt 22 and the recording medium 29 which is transferred from the tray 29a. The transfer roller 28 is provided with the body 21 so as to be able to shift upwardly. The developing roller 27 makes an image to be printed at the recording medium 29 onto the photosensitive belt 22 by toners thereto adhering. Then, the transfer roller 28 transfers the image comprising toners which is formed onto the photosensitive belt 22 to the recording medium 29.
The photosensitive belt 22 provided with the conventional electrophotographic printer is changed by the following processes. FIGS. 7A to 7D, 8A, and 8B show the exchange processes of the photosensitive belt 22.
As shown in FIG. 7A, the developing roller 27 shifts downwardly, as indicated by the arrow F. Then, the transfer roller 28 shifts upwardly, as indicated by the arrow G. Thereby, the photosensitive belt 22 does not contact with the developing roller 27 and the transfer roller 28, as shown in FIG. 7B.
After that, the driving roller 25 shifts toward the driving roller 24, as indicated by the arrow H in FIG. 7C. Thereby, the tension of the photosensitive belt 22 lossens. Then, the photosensitive belt 22 is removed from the printer through the opening formed at the front of the printer by peeling the photosensitive belt 22 from the belt driver 31, as indicated by the arrow I in FIG. 7D.
In order to fit a new photosensitive belt 22 into the printer, the new photosensitive belt 22 is fitted with the printer by being passes through the opening formed at the front of the printer, and covering the belt driver 31. The driving roller 25 returns to the place where it was by shifting as indicated by the arrow K in FIG. 8B. Thereby, the photosensitive belt 22 becomes tense. Then, the developing roller 27 shifts upwardly as indicated by the arrow L, and sandwiches the photosensitive belt 22 together with the driving roller 26 opposite to the developing roller 27. The transfer roller 28 shifts downwardly as indicated by the arrow M, and sandwiches the photosensitive belt 22 together with the driving roller 23 opposite to the developing roller 28. The photosensitive belt 22 is exchanged by these processes.
However, in order to exchange the photosensitive belt 22 in the conventional electrophotographic printer, it is necessary to shift the developing roller 27, the transfer roller 28, etc., and members for shifting the developing roller 27, the transfer roller 28, etc. are needed. Therefore, the problem arises that the structure of the printer is complicated. In addition, the exchange method of the photosensitive belt 22 is also complicated.
It is therefore an object of the present invention to provide an electrophotographic image forming device which has a simple structure and in which a photosensitive belt or a transfer belt is easily exchanged, and an exchange method of a photosensitive belt and a transfer belt, which can be easily carried out.